/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.flowable.common.engine.api.query;

import java.util.List;

/**
 * Describes basic methods for querying.
 *
 * @author Frederik Heremans
 */
public interface Query<T extends Query<?, ?>, U extends Object> {

    enum NullHandlingOnOrder {
        NULLS_FIRST, NULLS_LAST
    }

    /**
     * Order the results ascending on the given property as defined in this class (needs to come after a call to one of the orderByXxxx methods).
     */
    T asc();

    /**
     * Order the results descending on the given property as defined in this class (needs to come after a call to one of the orderByXxxx methods).
     */
    T desc();

    T orderBy(QueryProperty property);

    T orderBy(QueryProperty property, NullHandlingOnOrder nullHandlingOnOrder);

    /**
     * Executes the query and returns the number of results
     */
    long count();

    /**
     * Executes the query and returns the resulting entity or null if no entity matches the query criteria.
     *
     * @throws org.flowable.common.engine.api.FlowableException when the query results in more than one entities.
     */
    U singleResult();

    /**
     * Executes the query and get a list of entities as the result.
     */
    List<U> list();

    /**
     * Executes the query and get a list of entities as the result.
     */
    List<U> listPage(int firstResult, int maxResults);
}
